Folding stair unit



FIG. 1 is a left side elevational view of a folding stair unit showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a right side elevational view with the step element partially closed; and,

FIG. 8 is a right side elevational view with the step element fully closed to storage position. 

The ornamental design for a folding stair unit, as shown. 